To manufacture plain wood lumbers, freshly cut wood logs undergo a series of transformations. Typically, the bark is first removed, then the cross-section of the wood log is transformed from a rounded shape to a cruciform shape. This shape transformation optimizes the number of wood lumbers that can be extracted from a given wood log. In a further step, wood lumbers are cut out of each of the cruciform shaped wood logs, and finally, the surfaces of the wood lumbers are trimmed to reduce roughness and splinters, and to obtain a consistent thickness throughout the length of the lumber.
The trimming step is generally carried out using one of more planer heads. A planer head has the general configuration of a large rotating wheel provided with a plurality of knives extending outwardly from its circumference. When a lumber passes about a planer head in rotation, the knives take off an outside layer of the wood lumber (typically a ¼ or ½ inch layer) thereby trimming and smoothing its surface. An example of a planer head 10 of the prior art is shown in FIGS. 1 to 3. In this prior art configuration, the planer head 10 includes a generally cylindrical body 12 having a centrally disposed bore 14 coinciding with an axis of rotation R1 of the planer head 10 (which is also its longitudinal axis). The body 12 is plain and typically made of machined steel. The body 12 includes a plurality of knife pockets 16 (best shown in FIG. 2) radially disposed and uniformly distributed on a crenelated curved face 18 defining the circumference of the body 12, as best shown in FIG. 2.
The knife pockets 16 each includes a first wall 15, and a second wall 17 spaced apart and opposing the first wall 15. The first wall 15 can be scalloped, while the second wall 17 is substantially flat. Each of the knife pockets 16 is configured to receive a corresponding knife 20 (only one knife 20 being drawn in the figures) and a knife holder 22 for holding the knife 20 into position during the operation of the planer head 10.
Each knife 20 includes a connection portion 24 receivable in a knife pocket 16 to connect to the body 12, and a cutting edge 26 extending from the connection portion 24 to trim the wood lumbers when the planer head 10 is rotated about the axis of rotation R1.
Knife holders 22 are typically longitudinal slender members that collaborate with clamping assemblies 30 to retain the knives 20 onto the body 12, where each knife holder 22 is operated by a corresponding one of the clamping assemblies 30 (best shown in FIG. 3).
As it will be appreciated by those skilled in the art, this planer head configuration suffers many drawbacks. The clamping assemblies 30 are independent of each other, and each knife holders 22 is operated by its unique and corresponding clamping assemblies 30. As such, when knives 20 must be installed, replaced or repositioned, the operations have to be repeated for each and every one of the clamping assemblies 30, which tends to make the replacement of the knives 20 burdensome and costly. Further, because each of the knife 20 is adjusted independently, they may not protrude radially from the pocket 16 equally, which may cause ovalization of the planer head 10.
In other examples of prior art planer heads, the clamping assemblies may be disposed somewhere else on the planer head, but still require a plurality of knife holders and a corresponding plurality of clamping or securing mechanism, which makes the maintenance of such planer heads cumbersome.
Therefore, there is a need for a planer head that will overcome at least one of the above-identified drawbacks.